You would be surprised how much a STOCK engine can take as far as rpm's and time. We have ran stone stock big blocks at 4-200 for up to 35-45 mins, with no issues. The current set of Dart 555's we just built that our going into my boat will likely see WOT for up to 20 25 mins at time.. Anything that makes HP usually burns some oil. Check out the new Seven Marine out board 557. It uses a GM 6.2 with a tvs blower on it.